Field of the Invention
The present invention is directed generally to fluid powered diaphragm pumps including air operated diaphragm pumps. More specifically, the present invention is directed toward mechanisms for controlling the speed or frequency of such diaphragm pumps and improved methods of speed control for diaphragm pumps. Still more specifically, the present invention relates generally to governors designed as original equipment or as retrofit equipment for diaphragm pumps.
Air-operated diaphragm pumps and fluid powered pumps are widely used for pumping liquids, solutions, viscous materials, slurrys and suspensions containing substantial amounts of solids. Typically, diaphragm pumps are operated under extreme operating conditions that vary. Specifically, the viscosity of the fluid being pumped can vary, particularly when the fluid is a suspension containing solids. The amount of solids in the suspension can vary thereby dramatically affecting the viscosity of the liquid being pumped. In other instances, the viscosity of liquids being pumped can vary depending upon temperature and inconsistencies in the contents of the solution. As a result of a changing viscosity, the head on the suction side of the pump and the back pressure on the pump discharge may all vary substantially. Still further, in a system that includes a number of dispensing stations, one or more of the dispensing stations may be taken out of service or a dispensing station may be added thereby varying the system head.
As a result in changes in the fluid viscosity, system head or back pressure, the frequency or speed of the pump will vary because the air or power fluid supplied to the pump will typically be supplied at a constant pressure. Often, it is undesirable to vary the speed of the pump. Specifically, operators normally desire to have the pump operate at a steady speed or steady stay condition.
Another problem encountered with fluid powered diaphragm pumps is the loss of air or power fluid when the pump runs dry due to the emptying of the sump or tank containing the fluid being pumped. Because most fluid powered diaphragm pumps do not include an automatic cut-off for the air or power fluid, the pump enters into a runaway condition which wastes the air or power fluid.
While governors for fluid powered diaphragm pumps are known from, e.g., U.S. Pat. No. 3,741,689, the teachings of which are incorporated herein by reference, such devices are complicated, difficult to install and not feasible for use as a retrofit or add-on feature to existing pumps.
Therefore, there is a need for an improved fluid powered diaphragm pump or a retrofit kit or add-on feature for fluid powered diaphragm pumps which will enable the speed of the pump to be automatically controlled in response to variances in the viscosity or system head and which will further enable the speed of the pump to be substantially reduced if not stopped in the event the pump runs dry. Due to the large number of fluid powered diaphragm pumps in current use, it would be extremely desirable to provide such a system which could be added to existing pumps at a minimal cost.